Display apparatus and method for producing the same

ABSTRACT

A display apparatus includes an array of fiber-type semiconductor light-emitting elements. Each of the fiber-type semiconductor light-emitting elements includes a layered structure having a first electrode layer, a second electrode layer, and a semiconductor light-emitting layer at least part of which is sandwiched by the first and second electrode layers, and a fiber for supporting the layered structure and for propagating light emitted from the light-emitting layer. The display apparatus also includes driving connectors including a switching element or a plurality of first and second conductive lines, which are electrically connected to the first and second electrode layers, respectively, for driving the plurality of the fiber-type semiconductor light-emitting elements.

This application is a Continuation Application of U.S. patentapplication Ser. No. 10/382,574 filed Mar. 7, 2003, currently pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display apparatus provided with anarray of fiber-type semiconductor light-emitting elements, and a methodfor producing such a display apparatus. The present invention can besuitably utilized for a mobile information terminal, a personalcomputer, a word processor, an amusement apparatus, educationalequipment, a television set, and other suitable display devices andapparatuses which are used by a number of persons, for example.

2. Description of the Related Art

Apparatuses for displaying images (pictures, data, or arrays of othertwo-dimensional information) fall into two broad categories:self-luminous type and non-luminous type. As a display apparatus of theself-luminous type, an apparatus (CRT or PDP) in which light anddarkness of the luminous brightness are obtained by collisions ofelectrons and plasmas with phosphors by adjusting a voltage or a currenthave been commercialized. For the purpose of using such a displayapparatus outdoors, a direct view apparatus having a much larger size inwhich a number of chips of light-emitting diodes (LED) aretwo-dimensionally arranged has been also practically used.

In the case of a display apparatus with such LED chips, the pixelpitches are larger than those of the CRT or PDP. For this reason,display apparatuses with a 30-inch to a 60-inch screen cannot realizehigh-definition display of XGA or more with full color. The reason whythe pixel pitches are large is that the size of an LED chip functioningas a pixel is large, i.e., about several millimeters. As describedabove, even if the display apparatus with LED chips is suitable as adisplay apparatus of very large size disposed outdoors, it is difficultfor a CRT or PDP to be substituted for such a display apparatus.

On the other hand, research and development of a self-luminous typedisplay apparatus using organic EL materials or inorganic EL materialshave constructively been performed. These display apparatuses aresuitable for higher definition, but the size thereof cannot be easilyincreased.

SUMMARY OF THE INVENTION

In order to overcome the problems described above, preferred embodimentsof the present invention provide a display apparatus suitable for higherdefinition with a self-luminous device such as LED, and a method forproducing the display apparatus.

According to a preferred embodiment of the present invention, a displayapparatus includes an array of fiber-type semiconductor light-emittingelements, each of the fiber-type semiconductor light-emitting elementsincluding a layered structure having a first electrode layer, a secondelectrode layer, and a semiconductor light-emitting layer at least partof which is sandwiched by the first and second electrode layers, and afiber for supporting the layered structure and for propagating lightemitted from the light-emitting layer.

Each of the fiber-type semiconductor light-emitting elements preferablyhas a wave guide structure that enables light to be transmitted along alongitudinal axis thereof and to be emitted from an end surface of thelight emitting fiber. The waveguide structure may include a core and acladding structure surrounding the core such that light generated andemitted by the semiconductor light emitting element described above ispropagated along the core to an end surface of the light emitting fiber.It is preferred that the core and the cladding layer are bothtransparent, but have different refractive indexes relative to eachother such that the differences in refractive indexes provides thedesired waveguide function for transmitting light from the end surfaceof the light emitting fiber.

The light emitting fiber may also have other waveguide structures suchas a structure including a transparent fiber portion and a reflectivelayer, such as metal film, surrounding the transparent fiber portion.The transparent fiber portion can have a uniform refractive index. Withthis structure, light generated and emitted by the semiconductor lightemitting element is confined by the outer reflective layer andpropagates along the fiber. In this case, the reflective layer functionslike a cladding layer described above.

The display apparatus also includes driving connectors for connectingthe plurality of fiber-type semiconductor light-emitting elements to adriving device or circuit. The driving connector may include a pluralityof first and second conductive lines connected to first and secondelectrode layers, respectively, or switching elements for selectivelyconnecting at least one of the first and second electrode layers in thefiber-type semiconductor light-emitting element to a driving circuit.

The fiber-type semiconductor light-emitting elements are preferablyarranged in a matrix of rows and columns. In such a configuration, eachof the plurality of first conductive lines mutually connects the firstelectrode layers of a plurality of fiber-type semiconductorlight-emitting elements belonging to a corresponding row, and each ofthe plurality of second conductive lines mutually connects the secondelectrode layers of a plurality of fiber-type semiconductorlight-emitting elements belonging to a corresponding column. It ispreferred that a pattern of conductive films functions as the first andsecond conductive lines. The pattern of conductive films may be formedon a substrate used to contain the fibers, as described later.

In the configuration using a switching element as the driving connector,it is preferred that the switching element is a thin film transistorthat is formed as part of the layered structure of the fiber-typesemiconductor light-emitting elements.

An end surface of the array of the fiber-type semiconductorlight-emitting elements is preferably disposed in a positioncorresponding to a pixel.

Also, it is preferable that the layered structure is arranged around thefiber so as to surround the fiber.

In a preferred embodiment, the layered structure of each of thefiber-type semiconductor light-emitting elements includes a holecarrying layer, a light-emitting layer, and an electron carrying layerwhich are laminated on each other to form the layered structure.

The semiconductor light-emitting layer is preferably formed from amaterial which emits light selected from three primary colors of light,such that an end surface of the array of the fiber-type semiconductorlight-emitting element can display a full-color image.

In another preferred embodiment, each of the fiber-type semiconductorlight-emitting elements includes three kinds of semiconductorlight-emitting layers for emitting light of three primary colors,respectively, such that an end surface of the array of the fiber-typesemiconductor light-emitting elements can display a full-color image.

Alternatively, the semiconductor light-emitting layer may preferably beformed from a material which emits white light. In such a configuration,a color filter is disposed on an outside of an end surface of the arrayof the fiber-type semiconductor light-emitting elements.

In yet another preferred embodiment, the semiconductor light-emittinglayer is preferably formed from a material which emits white light, andthe fiber is provided with an element that functions as a color filter.

It is preferable that the fiber-type semiconductor light-emittingelement is a light-emitting diode, but other structures and elements canbe used for the fiber-type semiconductor light-emitting element. Forexample, the fiber-type semiconductor light-emitting element may also bea laser and may include a diffraction grating disposed on a surface ofthe fiber.

According to one preferred embodiment of the present invention, thedisplay apparatus preferably includes at least one substrate including aplurality of opening portions through each of which a respective fiberis inserted. In such a configuration, it is preferred that each of theopening portions has an inner diameter that corresponds to an outerdiameter of the fiber. The pattern of conductive films described abovemay preferably be formed on the substrate so as to define the pluralityof first and second conductive lines defining the driving connector.

In an alternative preferred embodiment, the display apparatus includes afirst substrate on which the plurality of first conductive linesextending in a first direction are disposed, and a second substrate onwhich the plurality of second conductive lines extending in a seconddirection intersecting the first direction are disposed.

It is preferred that the fiber is formed from a transparent materialwhich transmits visible light such as quartz, glass or plastic.

According to another preferred embodiment of the present invention, amethod for producing a display apparatus includes the steps of preparinga plurality of fiber-type semiconductor light-emitting elements, each ofthe plurality of fiber-type semiconductor light-emitting elementsincluding a layered structure having a first electrode layer, a secondelectrode layer, and a semiconductor light-emitting layer sandwiched bythe first and second electrode layers, and a fiber for supporting thelayered structure and for propagating light emitted from thelight-emitting layer, preparing at least one substrate having aplurality of opening portions through which the fiber-type semiconductorlight-emitting elements are inserted, and forming driving connectors tobe electrically connected to the first and second electrode layers ofthe fiber-type semiconductor light-emitting elements, and inserting thefiber-type semiconductor light-emitting elements into the openingportions of the at least one substrate.

It is preferred that the step of preparing the at least one substrateincludes a step of forming a conductive film on the substrate to definea plurality of first and second conductive lines electrically connectedto the plurality of first and second electrode layers, the conductivefilm blocking the opening portions of the substrate.

It is also preferable that the step of preparing the fiber-typesemiconductor light-emitting elements includes a step of growing thelight-emitting layer on the fiber while rotating the fiber, and/or, astep of growing the light-emitting layer on the fiber while rotating adeposition source of the respective light-emitting layer with respect tothe fiber.

Other features, elements, steps, characteristics and advantages of thepresent invention will become more apparent from the following detaileddescription of preferred embodiments of the present invention withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary as well as the following detailed description ofpreferred embodiments of the present invention will be better understoodwhen read in conjunction with the attached drawings. For the purpose ofillustrating the present invention, there is shown in the drawingsvarious embodiments which are presently preferred. It should beunderstood, however, that the present invention is not limited to theprecise arrangements and instrumentalities shown.

FIG. 1 is a sectional view illustrating part of a fiber-typesemiconductor light-emitting element used in a display apparatusaccording to a preferred embodiment of the present invention.

FIG. 2 is a perspective view illustrating an array of the fiber-typesemiconductor light-emitting elements used in the display apparatusaccording to a preferred embodiment of the present invention.

FIGS. 3A and 3B are plan views illustrating conductive line layouts of asubstrate used in the display apparatus according to a preferredembodiment of the present invention.

FIG. 4A is a perspective view illustrating a fundamental configurationin a first preferred embodiment of the display apparatus of the presentinvention.

FIG. 4B is a plan view schematically illustrating an arrangement ofpixels in the display apparatus of FIG. 4A.

FIG. 5 is a perspective view illustrating a fundamental configuration ina second preferred embodiment of the display apparatus of the presentinvention.

FIG. 6 is a perspective view illustrating a fundamental configuration ina third preferred embodiment of the display apparatus of the presentinvention.

FIG. 7 is a schematic plan view showing a layout of an active matrixsubstrate used in a fourth preferred embodiment of the display apparatusof the present invention.

FIG. 8 is a sectional view illustrating part of a fiber-typesemiconductor light-emitting element with which a switching element isintegrated in the fourth preferred embodiment of the display apparatusof the present invention.

FIG. 9 is a view illustrating part of a fiber-type semiconductorlight-emitting element which emits laser light from an end surfacethereof in a fifth preferred embodiment of the display apparatus of thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the inventive display apparatuswill be described with reference to the accompanying drawings.

The display apparatus of the present invention preferably includes anarray of fiber-type semiconductor light-emitting elements. Thefiber-type semi-conductor light-emitting elements are connected to adriving device or circuit through driving connectors, which may includeconductive lines or switching elements connected to electrode layers ofthe respective fiber-type semiconductor light-emitting elements. Thefiber-type semiconductor light-emitting elements preferably have awaveguide structure that allows light generated therein to be propagatedalong a length thereof and emitted from end surfaces of the fiber-typesemiconductor light-emitting elements. In a preferred embodiment, endsurfaces of the fiber-type semiconductor light-emitting elements aretwo-dimensionally arranged (i.e., in a matrix of rows and columns), whenthe end surfaces are viewed by a monitor. Arbitrary images are displayedby the light emitted from the respective end surfaces of the fiber-typesemiconductor light-emitting elements.

Each of the fiber-type semiconductor light-emitting elements includes afiber through which light can be transmitted (an optical fiber, forexample) and a layered structure disposed on the fiber. The layeredstructure has various layers including a semiconductor light-emittinglayer, and first and second electrode layers for causing a current toflow to the layers included in the layered structure. The firstelectrode layer and the second electrode layer function as an anode anda cathode, respectively, and the first and second electrode layerssandwich the semiconductor light-emitting layer at least along a portionthereof.

When an appropriate voltage is applied from a plurality of fiber-typesemiconductor light-emitting elements arranged in an array to the firstand second electrode layers of an arbitrarily selected light-emittingelement, recombination is caused between a hole and an electron injectedinto a semiconductor light-emitting layer of the light-emitting element,thereby realizing emission of light having a desired wavelength band.The light emitted from the semiconductor light-emitting layereffectively propagates through the fiber, and typically radiates via thewaveguide structure of the fiber and is emitted from one end surface ofthe fiber to the outside. The light emitted from the end surface of thefiber contributes to the display of images. The end surfaces of thefibers arranged in the array configuration function as pixels or pictureelements, respectively. The method for emitting light from a fiber isnot limited to this preferred embodiment. Alternatively, light may beemitted to the outside from a specified portion provided in a sidesurface of the fiber, and the light may be used for the display ofimages.

In the case where light-emitting surfaces of fibers (typically, “fiberend surfaces”) are arranged in a matrix of rows and columns, lightemission of the respective fiber-type semiconductor light-emittingelements is controlled by using a known driving circuit, so as todisplay a desired image.

When the display apparatus of a preferred embodiment of the presentinvention is configured to operate via passive driving, drivingconnectors including a plurality of first conductive lines respectivelyconnected to the first electrode layers of the fiber-type semiconductorlight-emitting elements and a plurality of second conductive linesrespectively connected to the second electrode layers are electricallyconnected to a driving circuit, so that the light emission of therespective fiber-type semiconductor light-emitting elements can becontrolled by the driving circuit. As the driving circuit, a knowncircuit used in a liquid crystal display apparatus, an organic ELdisplay apparatus, or other suitable driving device or circuit can beused.

On the contrary, if a switching element such as a TFT, which defines adriving connector, is assigned to each fiber-type semiconductorlight-emitting element, the display apparatus of another preferredembodiment of the present invention can be driven by active matrixdriving. In such a case, if the switching element such as a TFT isprovided on the fiber, processes of producing a display apparatus byusing fiber-type semiconductor light-emitting elements can besimplified, and the size of the apparatus can be easily reduced.

The layered structure of the fiber-type semiconductor light-emittingelement has a structure preferably functioning as an LED or a laserdiode. A semiconductor light-emitting layer and the other layers arepreferably formed from an organic material or an inorganic materialappropriately selected in accordance with required characteristics suchas a wavelength of emitted light. In order to form a semiconductor layerof good quality on a fiber, it is preferred that each layer is formed byusing an organic EL material which will be described in detail later.

Hereinafter, specific preferred embodiments of the display apparatus ofthe present invention will be described with reference to theaccompanying drawings.

First Preferred Embodiment

The first preferred embodiment will be described with reference to FIGS.1, 2, 3, 4A, and 4B.

The first preferred embodiment preferably includes a fiber-typesemiconductor light-emitting element 10 as shown in FIG. 1. Thefiber-type semiconductor light-emitting element 10 in FIG. 1 preferablyincludes a glass fiber 1 having a diameter of about 0.5 mm, and alayered structure 2 formed around the glass fiber 1 so as to surroundthe glass fiber 1. The layered structure 2 in FIG. 1 includes a firstelectrode layer (an anode) 3, a hole carrying layer 4, a light-emittinglayer 5, an electron carrying layer 6, and a second electrode layer (acathode) 7. In this preferred embodiment, the layered structure 2constitutes an organic light-emitting diode (OLED).

The glass fiber 1 preferably has a wave guide structure that enableslight to be transmitted along a longitudinal axis thereof and emittedfrom an end surface of the light emitting fiber 1. The waveguidestructure may include a core and a cladding structure surrounding thecore such that light generated and emitted by the semiconductor lightemitting element described above is propagated along the core to an endsurface of the light emitting fiber. It is preferred that the core andthe cladding layer are both transparent, but have different refractiveindexes relative to each other such that the differences in refractiveindexes provides the desired waveguide function for transmitting lightfrom the end surface of the light emitting fiber. For example, the glassfiber 1 is preferably constituted by a core portion with a relativelyhigh refractive index, and a clad portion with a relatively lowrefractive index. The clad portion surrounds an outer circumference ofthe core portion. It is preferred that a coating for protection (notshown) be formed around the clad portion, but the coating is notnecessarily required.

The light emitting fiber 1 may also have other waveguide structures suchas a structure including a transparent fiber portion and a reflectivelayer, such as metal film, surrounding the transparent fiber portion.The transparent fiber portion can have a uniform refractive index. Withthis structure, light generated and emitted by the semiconductor lightemitting element is confined by the outer reflective layer andpropagates along the fiber. In this case, the reflective layer functionslike a cladding layer described above.

As a fiber used in preferred embodiments of the present invention, anoptical fiber which is usually used for optical communications maypreferably be used. Alternatively, any other type of fiber can be used.The fiber in the present invention is not used for performinglong-distance transmission of light signals. For this reason, it isunnecessary to rigorously limit the materials and the design of thestructure of the fiber in view of problems such as transmission loss ordispersion. Therefore, it is possible to realize the display apparatusof various preferred embodiments of the present invention even if afiber to be used has a configuration in which the circumference of afiber-like member with uniform distribution of refractive index iscovered with a reflection film or other suitable element, for example.Alternatively, instead of the glass fiber, a fiber made of anothersuitable material (a plastic fiber, for example) may be used.

The first electrode layer 3 of the light-emitting element in thispreferred embodiment is preferably formed of an IZO (IN₂O₃—ZnO) layer,for example. The IZO layer is deposited around the fiber by RFsputtering, for example. The hole carrying layer 4 is preferably formedby a P-TPD (TPD-based polymer) layer, for example. The P-TPD layer isgrown from an MDC solution by dipping. The light-emitting layer 5 andthe second electrode layer 7 are preferably formed of an Alq3 layer andan MgAg layer, respectively. These layers can preferably be formed byvacuum evaporation while rotating the fiber.

In the case where the layered structure has a fiber shape, various filmshaving substantially uniform thickness or characteristics in an axisdirection of the fiber can be cylindrically deposited around the fiber.Therefore, it is easy to increase an effective area of thelight-emitting area without increasing the outer diameter of the fiber.However, in the manufacturing process, it is preferable that a pluralityof isolated light-emitting elements, each having a layered structure,are formed on a fiber having a sufficient length, and then the fiber iscut and separated into fiber-type semiconductor light-emitting elementshaving a predetermined length by a method described later. The layeredstructure is not uniformly formed in the axial direction of the fiber,but various device structures can be realized in various combinations ofa plurality of layers having predetermined patterns. It is preferredthat a step of patterning the film deposited on the fiber byphotolithography and etching is performed to achieve the desired layeredstructure on the fiber.

FIG. 2 schematically shows an array of the fiber-type semiconductorlight-emitting elements 10 used in the display apparatus of the presentpreferred embodiment. Each of the fiber-type semiconductorlight-emitting elements 10 constituting the array preferably has theconfiguration described with reference to FIG. 1. In an example shown inFIG. 2, a number of fiber-type semiconductor light-emitting elements 10are bundled, and mutual positional relationships are fixed by anadhesive or other suitable fixing element. For fixing by an adhesive, anadhesive polymer such as an epoxy resin may be preferably used.

The bundle of the fiber-type semiconductor light-emitting elements 10shown in FIG. 2 is sliced, so as to be divided into a plurality ofdevice blocks each having a predetermined length. The respective deviceblocks are used in combination with a substrate which will be describedlater, so as to constitute a display apparatus.

When a bundle of fiber-type semiconductor light-emitting elements 10which are relatively long (which have a length of about 50 cm or more,for example) is to be divided into the above-described device blocks,the bundled fibers are preferably cut so as to have a predeterminedlength. The length of fiber-type semiconductor light-emitting elementused for the display apparatus is typically set in the range of aboutseveral centimeters to about several tens of centimeters. In thispreferred embodiment, after the longer fiber-type semiconductorlight-emitting elements 10 are bundled, the fibers are cut to be short.Alternatively, after the fibers are cut to be short, a plurality offibers in the cut condition may be bundled. Alternatively, the step ofbundling the fibers is omitted, and individual fibers may be insertedinto opening portions of the substrate which will be described later.

In the case where a glass fiber is used for the fiber-type semiconductorlight-emitting element 10, a flaw may occur on a clad surface of thefiber by using a super hard blade of diamond, ceramics, or othermaterial for performing the step of cutting the fibers. Thereafter, abending stress is applied to the fiber, thereby cutting the fiber sothat a surface that is substantially perpendicular to the fiber axis isexposed as a cut surface (an end surface). A grinding process maypreferably be performed on the end surface of the fiber, so as to removeor correct a burr or a chip formed in the vicinity of the end surfaceduring the cutting step.

On the contrary, in the case where a plastic fiber is used, after thecutting process, a finishing process of smoothing the cut surface (theend surface) of the fiber is performed, as necessary. The finishingprocess can be performed by grinding or hot plating. In the hot platingprocess, an end portion of the fiber is pressed against a heated metalmirror surface, so that the flatness of the metal mirror surface istransferred to the end surface of the fiber. In order to increase theluminance of the light emitted from the fiber, it is desired that theend surface of the fiber be smoothed. Alternatively, for other purposes,the end surface of the fiber may be processed so as to be concave orconvex. Alternatively, a process of applying a property of lightdiffusion to the end surface of the fiber may be performed.

FIGS. 3A and 3B respectively show a substrate 33 in which a plurality ofconductive lines (interconnects or driving connectors) 31 required fordriving the fiber-type semiconductor light-emitting elements 10 areformed. In the substrate 33, opening portions (holes) 32 arranged in amatrix of rows and columns are formed. The fibers are inserted into theopening portions 32. Thus, each of the opening portions 32 has an innerdiameter (about 0.5 mm, for example) that substantially corresponds tothe outer diameter of the fiber. The conductive lines 31 on thesubstrate 33 shown in FIG. 3A are extended in a row direction. Theconductive lines 31 on the substrate 33 shown in FIG. 3B are extended ina column direction. The conductive lines formed on the two substratesmutually intersect at right angles, so that passive-type driving can beperformed.

A width of each conductive line 31 is preferably substantially equal tothe inner diameter of each opening portion 32. Each conductive line 31is electrically connected to the electrode layer 3 or 7 of thefiber-type semiconductor light-emitting element 10 inserted in thecorresponding opening portion 32. Thus, the corresponding electrodelayer 3 or 7 is connected to a driving circuit which is not shown.Before the fiber-type semiconductor light-emitting element 10 isinserted into the opening portion 32 of the substrate 33, the conductiveline 31 is formed so as to block the opening portions 32 of thesubstrate 33. One end of each fiber-type semiconductor light-emittingelement 10 is inserted into a corresponding opening portion 32 of thesubstrate 33, and the electrode layer 3 or 7 of the fiber-typesemiconductor light-emitting element 10 becomes in contact with theconductive line 31 on the substrate 33, so that the electrical contactof the electrode layer 3 or 7 with the conductive line 31 can beensured. In order to smoothly insert the fiber-type semiconductorlight-emitting element 10 into the opening portion 32 of the substrate33, an end portion opposite to the light-emitting end surface of thefiber may be sharpened.

FIGS. 4A and 4B show structure in which three kinds of fiber-typesemiconductor light-emitting elements 10R, 10G, and 10B corresponding tothree primary colors of light R, G, and B are combined with thesubstrates 33 shown in FIGS. 3A and 3B, respectively. A light-emittinglayer of the fiber-type semiconductor light-emitting element 10R for redmay preferably be formed by using a combination of Alq3 (a hostmaterial) and dicyanoquinodimethane (a dopant material). Similarly, alight-emitting layer of the fiber-type semiconductor light-emittingelement 10G for green may preferably be formed by using a combination ofAlq3 (host material) and quinacridon (a dopant material), and alight-emitting layer of the fiber-type semiconductor light-emittingelement 10B for blue may preferably be formed by using a combination ofdistilallylene derivative (a host material) and styrylamine derivative(a dopant material).

In the case where the light-emitting layers are formed from inorganiccompounds, ZnS:Mn for red, ZnS:TbOF for green, and SrS:Cu, SrS:Ag, orSrS:Ce for blue may be used, for example.

In the examples shown in FIGS. 4A and 4B, one pixel is preferablyconstituted by three fiber-type semiconductor light-emitting elements10R, 10G, and 10B for R, G, and B. The driving of the respectivefiber-type semiconductor light-emitting elements 10R, 10G, and 10B isperformed by a driving circuit (not shown) connected to the conductiveline 31 on the substrate 33. Gradation display is performed by timedivision in which duty ratio of light-emitting time is controlled.

The size of display screen, the pixel pitches, and other physicalcharacteristics and features can be arbitrarily set. In an exemplarycase where an XGA display with pixel pitches of 1024×3 (RGB)×768 isprovided, pixels can be arranged at pitches of approximately 330 μm byusing fibers each having an outer diameter of about 200 μm, for example.

Second Preferred Embodiment

Next, the second preferred embodiment of the present invention will bedescribed with reference to FIG. 5.

In the first preferred embodiment shown in FIGS. 4A and 4B, threefiber-type semiconductor light-emitting elements 10R, 10G, and 10B forR, G, and B are preferably used for each pixel. In the second preferredembodiment, as shown in FIG. 5, a fiber-type semiconductorlight-emitting element 10′ preferably has three semiconductorlight-emitting elements for R, G, and B disposed on one fiber. In theexemplary configuration shown in FIGS. 4A and 4B, three kinds of lightemissions R, G, and B are generated on respectively different fibers. Inthe second preferred embodiment, light having full color can be obtainedfrom one fiber-type semiconductor light-emitting element 10′.Accordingly, the definition can be three times as high in the secondpreferred embodiment as compared to that of the first preferredembodiment.

In the first preferred embodiment, the arranged pitches of thefiber-type semiconductor light-emitting elements 10 are large ascompared with the fiber diameter. For this reason, in the case where adisplay apparatus of relatively large size is produced by usingdifferent fiber-type semiconductor light-emitting elements for R, G, andB, and an image is viewed in a position close to the screen, the pixelpitches may become so large that they cannot be ignored as compared withthe spatial resolution of vision of a human being. In such a case,spatial mixing is not sufficiently achieved, and the colorreproducibility may be disadvantageously deteriorated. However, in thispreferred embodiment, light of a desired color is emitted from eachfiber-type semiconductor light-emitting element 10′, so that it isadvantageous that the color reproducibility is not deteriorated, even ifthe pixel pitches are large (i.e., even if the pixels are coarselyarranged).

The three kinds of semiconductor light-emitting elements for R, G, and Bon one fiber do not necessarily emit light always simultaneously.Alternatively, for the purpose of reducing the electric powerconsumption, or other purposes, light may be emitted in a timedivisional manner. If the light emission of R, G, and B is performed inan appropriate field cycle, color reproduction sufficient for eyes of ahuman being can be realized.

Third Preferred Embodiment

Next, the third preferred embodiment of the present invention will bedescribed with reference to FIG. 6.

Each fiber-type semiconductor light-emitting element 10 used in adisplay apparatus of this preferred embodiment can emit white color. Inorder to obtain a color image from white light, a color filter 60 isdisposed on the light-emitting side in this preferred embodiment.

In the case where such a white light-emitting layer is formed from amacro molecular material, a red, green, or blue fluorescence dye may bedispersed in poly(N-vinylcarbazole (PVK) as a host material, forexample. In order to increase luminous efficiency, it is preferred thatpolyalkylthiophene derivative which is a conductive polymer be used fora buffer layer on an anode side, and a cesium metal be used as anelectron injecting layer on a cathode side.

On the contrary, in the case where the white light-emitting layer isformed from a low molecular material, a ZnBTZ complex may be used, forexample. Alternatively, a lamination of TPD (aromatic diamine)/p-EtTAZ(1,2,4-triazole derivative)/Alq may be used.

In the case where the white light-emitting layer is formed from aninorganic material, the white light can be obtained by mixing blue lightemitted from a ZnSe-based light-emitting layer with light (green to red)emitted from a ZnSe substrate, for example.

In the above-described example, a conductive line 31 on a substrate 33is directly connected to an electrode layer 3 or 7 of the fiber-typesemiconductor light-emitting element 10.

Alternatively, a switching element such as a TFT may be disposed betweenthe conductive line 31 and the electrode layer 3 or 7. In this preferredembodiment, the color filter is preferably disposed on the outside ofthe end surface of the fiber. Alternatively, a filtering function may beadded to the fiber. When an appropriate impurity or pigment is mixedinto the fiber so as to absorb light of a specified wavelength band, thefiber functions as a color filter. Thus, it is unnecessary toadditionally provide and arrange a color filter.

In this preferred embodiment, a color filter substrate may preferably beused. Alternatively, another type of optical film (a light scatteringsheet, for example) may be appropriately used together with the colorfilter substrate.

Fourth Preferred Embodiment

Next, the fourth preferred embodiment of the present invention will bedescribed with reference to FIG. 7.

FIG. 7 shows a layout configuration of an active matrix substrate usedin this preferred embodiment. In this preferred embodiment, in order toperform active matrix driving, two kinds of conductive lines (a gate busline and a source bus line) and a TFT are preferably formed on thesubstrate.

A gate electrode 12 of each TFT formed on the active matrix substrateshown in the figure is connected to a corresponding gate bus line GL,and a source electrode 13 is connected to a corresponding source busline SL. The TFT switches between conductive and non-conductive statesin accordance with the level of a gate signal applied to the gate busline GL. When the TFT is in the conductive state, an electric potentialon the source bus line SL is applied to a second electrode layer 7 of afiber-type semiconductor light-emitting element 10 via a drain electrode9. The gate bus line GL and the source bus line SL are respectivelyconnected to driving circuits (a source driver or a gate driver) whichare not shown.

FIG. 8 shows a sectional configuration of a fiber-type semiconductorlight-emitting element 20 in which the above-described TFT is not formedon a substrate, but on a fiber. In the example shown in FIG. 8, theconfiguration for TFT is added to the configuration of the fiber-typesemiconductor light-emitting element 10 shown in FIG. 1. Specifically,the configuration includes a layer insulation film 8 formed on thesecond electrode layer 7, a drain electrode 9 which is in contact withthe second electrode layer 7 via an opening portion of the layerinsulation film 8, an organic semiconductor layer 14 formed on the layerinsulation film 8, a gate insulation film 11 formed on the organicsemiconductor layer 14, a gate electrode 12 formed on the gateinsulation film 11, and a source electrode 13 which is in contact withthe organic semiconductor layer 14 in a region where the gate electrode12 is not located.

In the configuration shown in FIG. 8, the second electrode layer 7 iselectrically in contact with the drain electrode 9. In accordance withthe electrical potential applied from the gate electrode 12 to theorganic semiconductor layer 14, a conductive channel is formed betweenthe drain electrode 9 and the source electrode 13. As a result, adesired electrical potential is applied from a TFT connected to theselected gate bus line GL to the second electrode layer 7, so that acurrent flows between the first electrode layer 3 and the secondelectrode layer 7. Thus, light required for the display is generated inthe light-emitting layer 5, and the light propagates through the fiber1.

In this preferred embodiment, three substrates shown in FIG. 3 arepreferably prepared. In each of the substrates, a conductive lineconnected to the first electrode layer 3, a gate bus line connected tothe gate electrode 12, and a source bus line connected to the sourceelectrode 13 are formed. It is understood that the first electrode layer3 is a common electrode which is common to the respective light-emittingelements, so that it is unnecessary to have a pattern which is dividedinto a plurality of portions as in the conductive line 31 shown in FIG.3.

When the fiber-type semiconductor light-emitting element 20 is insertedinto an opening portion of each substrate, the electrode on the fiberand the conductive line on the substrate are mutually connected.Accordingly, a circuit similar to the circuit shown in FIG. 7 is formed,so that it is possible to perform active matrix driving.

It is preferred that the gate electrode 12 and the source electrode 13are arranged in a ring manner around the fiber, similarly to the firstelectrode layer 3. With such a configuration, a contact area with theconductive line on the substrate is increased, so that a contactresistance is reduced. Moreover, a channel width of a transistor isincreased, so that the driving force is increased. An inner diameter ofthe opening portion formed in each substrate is appropriately set inaccordance with an outer diameter of the electrode layer which isarranged in a ring manner.

In this preferred embodiment, one switching element such as a TFT ispreferably disposed on one fiber. Alternatively, the number of switchingelements assigned to one light-emitting element may be two or more. Inthe display apparatus having a configuration shown in FIG. 5, forexample, six (=2×3) or more switching elements may be disposed on onefiber.

The configuration in which the switching elements such as TFTS areformed on the fiber is arbitrarily selected. For example, a cylindricalsemiconductor layer may be separated into a plurality of portions whichare symmetric with respect to the axis, and a plurality of TFTS arearranged on the same circumference. Alternatively, the respectiveswitching elements disposed on the same fiber may be connected, so as toconstitute a circuit having some function. In such a case, a conductiveline for mutually connecting the switching elements is preferably alsoformed on the fiber.

Fifth Preferred Embodiment

Next, the fifth preferred embodiment of the present invention will bedescribed with reference to FIG. 9.

A display apparatus of this preferred embodiment is constituted by usinga fiber-type semiconductor light-emitting element 30 shown in FIG. 9.The fiber-type semiconductor light-emitting element 30 preferablyincludes a grating (diffraction grating) 90 for forming a resonatorstructure required for laser oscillation on a fiber.

The fiber-type semiconductor light-emitting element 30 in FIG. 9 has astructure, similar to the fiber-type semiconductor light-emittingelement 10 in FIG. 1, in which a first electrode layer, a hole carryinglayer, a light-emitting layer, an electron carrying layer, and a secondelectrode layer are layered on the fiber in this order. When a voltageof a threshold value or more is applied across the first electrode and asecond electrode, laser light emitted from the light-emitting layer andoscillating in the resonator is combined in the fiber, and then thelaser light is radiated from an end surface of the fiber. By adjustingthe grating period of the grating 90 formed on the fiber, theoscillating wavelength of laser can be selected to within apredetermined range. The grating 90 is produced in the following manner.After an interference pattern is formed by using optical interferencewith respect to a photo resist applied on the fiber, etching for thefiber surface is performed.

The fabrication of the layered structure of the fiber-type semiconductorlight-emitting element 30 in FIG. 9 can be performed in the followingmanner, for example. First, a fiber with a surface on which an ITO film(an anode layer) having a thickness of, for example, about 150 nm isprovided is prepared, and the fiber is washed for approximately 30seconds using oxygen plasma. Next, on the ITO film,copoly[3,3′-hydroxytetraphenylebenzidine/diethyleneglycol]carbonate isdeposited as a hole carrying material, thereby forming a hole carryinglayer having a thickness of about 220 nm. Thereafter,diamino-distyrylbenzene (DADSB) as an organic pigment material isdeposited in a vacuum on the hole carrying layer. Next, a light-emittinglayer having a thickness of about 100 nm is formed. Moreover, anoxadiazole (OXD) derivative is deposited in a vacuum, so that anelectron carrying layer having a thickness of about 240 nm is formed. Onthe electron carrying layer, a Mg.Ag alloy is deposited in a vacuum, anda cathode layer having a thickness of about 200 nm is formed. Therefractive index of the hole carrying layer formed by theabove-described method is about 1.75, the refractive index of th about2.11, and the refractive index of the electron carrying layer is about1.93.

Next, a solution in whichcopoly[3,3′-hydroxytetraphenylbenzidine/diethylene glycol]carbonate ofabout 50 mg and the above-mentioned tris(4-bromophenyl)ammonium.hexachloroantimonate (TBAHA) of 5 mg are dissolved indichloromethane of approximately 1 mL is spin coated at revolution ofabout 1000 rpm. Then, heating is performed at 80° C. for about 1 hour,so as to remove solvent, thereby forming a hole carrying layer having afilm thickness of approximately 650 nm.

The configuration and the manufacturing method of the fiber-typesemiconductor light-emitting element 30 used in this preferredembodiment are not limited to the above-described examples.

When a display apparatus is constituted by using the fiber-typesemiconductor light-emitting element 30 which performs laseroscillation, high luminance can be realized with low power consumption.In addition, instead of direct view type, the display apparatus can beused as a display apparatus of a projection type.

According to the display apparatus of various preferred embodiments ofthe present invention, the display is performed by using an array offiber-type semiconductor light-emitting elements, so that high luminanceand high visibility can be realized with a relatively simpleconstruction and with low power consumption.

In preferred embodiments of the present invention, the layered structurefor light emission is preferably provided on the fiber, so that it iseasy to enlarge an area of effective light-emitting region of thelight-emitting layer, and high luminance can be easily realized withoutreducing the degree of integration. Especially, the present inventioncan be applied to the projection type display apparatus in which laseroscillation is performed in light-emitting elements.

The fiber-type semiconductor light-emitting element used in preferredembodiments of the present invention can be designed and modified duringthe production process, so that it is superior in quantity production,and the handling is easy. The length can be freely set by cutting thefiber, so that it is possible to apply various formations to the displaydevice.

While the present invention has been described with reference to variouspreferred embodiments thereof, it will be apparent to those skilled inthe art that the disclosed invention may be modified in numerous waysand may assume many embodiments other than those specifically set outand described above. Accordingly, it is intended that the appendedclaims cover all modifications of the present invention which fallwithin the true spirit and scope of the invention.

1. A display apparatus comprising: an array of fiber-type semiconductorlight-emitting elements, each of the fiber-type semiconductorlight-emitting elements including a layered structure having a firstelectrode layer, a second electrode layer, and a semiconductorlight-emitting layer at least part of which is sandwiched by the firstand second electrode layers, and a fiber for supporting the layeredstructure and for propagating light emitted from the light-emittinglayer; and a plurality of driving connectors electrically connected toat least one of the plurality of first and second electrode layers forconnecting the array of fiber-type semiconductor light-emitting elementsto a driving circuit; wherein the layered structure is arranged aroundthe fiber so as to surround the fiber; the plurality of drivingconnectors includes a plurality of first conductive lines electricallyconnected to the first electrode layers and a plurality of secondconductive lines electrically connected to the second electrode layers;and the fiber-type semiconductor light-emitting elements are arranged ina matrix of rows and columns, each of the plurality of first conductivelines mutually connects the first electrode layers of a plurality offiber-type semiconductor light-emitting elements belonging to acorresponding row, and each of the plurality of second conductive linesmutually connects the second electrode layers of a plurality offiber-type semiconductor light-emitting elements belonging to acorresponding column.
 2. The display apparatus of claim 1, wherein lightgenerated in each of the fiber-type semiconductor light-emittingelements is propagated along a length of the fiber and emitted from endsurfaces of the fiber.
 3. The display apparatus of claim 1, wherein thefiber of each of the fiber-type semiconductor light-emitting elementshas a waveguide structure that allows light generated therein to bepropagated along a length thereof and emitted from end surfaces of thefiber-type semiconductor light-emitting elements.
 4. The displayapparatus of claim 1, wherein the plurality of driving connectorsincludes a plurality of switching elements electrically connected to atleast one of the plurality of first electrode layers and the pluralityof second electrode layers.
 5. The display apparatus of claim 4, whereineach of the plurality of switching elements is a thin film transistorincluded in the layered structure.
 6. The display apparatus of claim 1,wherein an end surface of the array of the fiber-type semiconductorlight-emitting elements is disposed in a position corresponding to apixel.
 7. The display apparatus of claim 1, wherein the layeredstructure includes a hole carrying layer, a light-emitting layer, and anelectron carrying layer which are disposed on top of each other todefine the layered structure.
 8. The display apparatus of claim 1,wherein each of the fiber-type semiconductor light-emitting elements isone of a light-emitting diode and a laser.
 9. A display apparatuscomprising: an array of fiber-type semiconductor light-emittingelements, each of the fiber-type semiconductor light-emitting elementsincluding a layered structure having a first electrode layer, a secondelectrode layer, and a semiconductor light-emitting layer at least partof which is sandwiched by the first and second electrode layers, and afiber for supporting the layered structure and for propagating lightemitted from the light-emitting layer; and a plurality of drivingconnectors electrically connected to at least one of the plurality offirst and second electrode layers for connecting the array of fiber-typesemiconductor light-emitting elements to a driving circuit; wherein adiffraction grating is disposed on a surface of the fiber; the pluralityof driving connectors includes a plurality of first conductive lineselectrically connected to the first electrode layers and a plurality ofsecond conductive lines electrically connected to the second electrodelayers; the fiber-type semiconductor light-emitting elements arearranged in a matrix of rows and columns, each of the plurality of firstconductive lines mutually connects the first electrode layers of aplurality of fiber-type semiconductor light-emitting elements belongingto a corresponding row, and each of the plurality of second conductivelines mutually connects the second electrode layers of a plurality offiber-type semiconductor light-emitting elements belonging to acorresponding column; the plurality of driving connectors includes aplurality of switching elements electrically connected to at least oneof the plurality of first electrode layers and the plurality of secondelectrode layers; and each of the plurality of switching elements is athin film transistor included in the layered structure.
 10. The displayapparatus of claim 9, wherein light generated in each of the fiber-typesemiconductor light-emitting elements is propagated along a length ofthe fiber and emitted from end surfaces of the fiber.
 11. The displayapparatus of claim 9, wherein the fiber of each of the fiber-typesemiconductor light-emitting elements has a waveguide structure thatallows light generated therein to be propagated along a length thereofand emitted from end surfaces of the fiber-type semiconductorlight-emitting elements.
 12. The display apparatus of claim 9, whereinan end surface of the array of the fiber-type semiconductorlight-emitting elements is disposed in a position corresponding to apixel.
 13. The display apparatus of claim 9, wherein the layeredstructure includes a hole carrying layer, a light-emitting layer, and anelectron carrying layer which are disposed on top of each other todefine the layered structure.
 14. The display apparatus of claim 9,wherein each of the fiber-type semiconductor light-emitting elements isone of a light-emitting diode and a laser.